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Advanced Kinetic Evolution of Oxidation Resistant Structures through Additive Manufacturing

Description:

TECHNOLOGY AREA(S): Air Platform 

OBJECTIVE: Model and understand the kinetic evolution of microstructures within High Entropy Alloys and Chemically Complex Alloys under complex thermal and kinetic additive manufacturing processes. This understanding will provide critical phase evolution and kinetic parameters for optimizing oxidation resistant and high strength ceramic and metallic materials for high temperatures. 

DESCRIPTION: High entropy and chemically complex alloys have exhibited tremendous potential for use in high strength and/or high temperature areas [1-4]. This includes uses for oxidation resistant and high strength applications. However critical information on phase interactions and evolution resulting from controlled thermal processes such as additive manufacturing remain unknown. Recent work has emphasized the potential for complex refractory oxides to facilitate sluggish oxidation kinetics at high temperatures, in many cases, without requiring the formation of classically protective, continuous oxide scales. While this is a promising observation, there exists a large foundational knowledge gap regarding the controlling mechanisms for phase evolution and the inherent structural/chemical oxide attributes. In addition, HEAs with concentrated compositions are designed to exploit the combination of precipitation strengthening, composite multi-phase strengthening, with novel deformation mechanisms in the matrix, such as deformation twinning (TWIP) effects and transformation induced plasticity (TRIP). This can potentially lead to higher strength, higher strain hardenability, and higher uniform elongation/tensile ductility. However the impact on composition and phase evolution is needed to properly optimize material combinations and identify potential valuable material combinations. This project is aimed at developing the models for phase interactions and evolutions within multi-principal element alloys under controlled thermal processing. Additive manufacturing offers novel processing approaches that control thermal processing within refined spatial regions, providing advanced diffusion control for developing composition gradients, non-equilibrium phases, and unique phase interactions. The use of these methods offers a tremendous opportunity to further develop our understanding of HEA phase evolution and behavior. 

PHASE I: The overall modeling approach for selected material combinations, including potential high entropy alloys/multiple principle element alloys will be developed for various additive manufacturing process windows. This includes identifying energies and interactions associated with materials processing, and determination of characterization steps for evaluating materials and microstructures (meso, continuum, and macro levels). The use of additive manufacturing to develop complex phases, composition gradients, and non-equilibrium phases will be evaluated. 

PHASE II: Selected materials will be produced and characterized to validate and verify phase evolution and kinetic microstructure models using the additive manufacturing processes identified from Phase 1. Mechanical properties will also be evaluated and modeled, employing deformation and/or oxidation mechanisms. Phase interactions and compositions will be characterized. The resulting basic understanding will be used to connect and optimize microstructure and mechanistic interactions. In addition, thermodynamic information will be provided for commercial computational data bases to enable equilibrium and metastable composition predictions. 

PHASE III: If warranted, the validated and verified models will be incorporated into crystal plasticity and material processing models for use by academic and industry partners for optimizing thermal processing. Basic science from energy and thermal conditions will be used to develop additive processing inputs for controlling phase evolution. 

REFERENCES: 

1. Miracle, D.B. , and O.N. Senkov, "A critical Review of High Entropy Alloys and Related Concepts", Acta Materialia 122, 488-511 (2017).; 2. Kumar, A., and M. Gupta, "An insight into evolution of light weight high entropy alloys: A review", Metals 6, (9) (2016).; 3. Soni, V, Gwalini, B, Senkov, O.N., Viswanathan, B, Alam, T, Miracle, D.B., Banergee, R, "Phase stability as a function of temperature in a refractory high-entropy alloy", JMR, v 33, iss 19, pp. 3235-3246.; 4. Senkov, O.N., Miracle, D.B., Chaput, K.J., and Couzinie, J.P., "Development and exploraiton of refractory high entropy alloys - A Review", JMR, v 33, iss 19, pp. 3092-3128.

KEYWORDS: Additive Manufacturing, High Entropy Materials, Multiprinciple Element Alloys 

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